Nothing can be more interesting, in a natural history point of view, than to watch the results upon large bodies of water, of attempts, more or less successful, to complete their drainage. Thus during the operations carried on for this purpose at Haarlem, there sprung up in the dry places of the more elevated parts an extraordinary quantity of plants and herbs, which were not seen in the country before they flowered and sent millions of seeds with their diminutive rocket, silky tails into the air. They were too minute to be seen upon grass, but the footpaths were covered with them, and a current of wind might carry them to distant regions, as the sand is carried from the coast of Africa into the track of the Brazilian packets, to such an extent as to make it uncomfortable to walk on deck. It is by no means, therefore, improbable that those errant seeds came from a foreign land, the native produce of other countries. Continuing my observations into the transit of seeds, I have found them to be the cause of shallow canals in England being full of heretofore unknown water-plants, to the extent of impeding navigation.
It is mentioned in the “Kosmos” of Humboldt, that the dust resulting from eruptions of the volcanic mountains in South America was observed in Spain. But if currents of wind thus carry seeds and other matters hundreds of miles through the air, no one can be surprised that the aquatic plants above alluded to floated to England through the air, from Holland; these plants, new to the land of their accidental adoption, bring with them a new corresponding animal life; in due time they come to maturity and die, and now Nature steps in to take up the task, and complete her work; her process is simple in appearance, most complex in its results: a malarious air—malarious at least to man—appears, as it may be, for the first time in the district, ascribed by medical men to every cause but the true one. In their anxiety to discover a cause, they fix on some antiquated drain, or cesspool, or ditch, by the margins of which many generations of a stout peasantry had lived and died; or they dive into the pump-well, and triumphantly exhibit infusoria, not unlikely engaged at the very moment in purifying the water: it never seems to have occurred to them that ferments only appear in certain combinations of the air—under circumstances which only occasionally occur, and that (which is most lamentable to think of, as in the case of London and the Thames) the evil is most frequently of man’s creation.[70]
The operations of nature when left to herself never vary; they may always be calculated on, foretold, anticipated; on this assured and irrefutable fact all science rests. It is only when man interferes and modifies the elements at work that nature seems to alter her processes; a disturbing agent has been thrust into the machinery, and the mischief it effects must either be counteracted or entirely overcome. So long as the Lake of Haarlem was a lake, or mere, so long were its banks healthy; but drain it partially, and you must be prepared for the result. There is no middle course; that which was once a lake or sea cannot be left in the condition of a putrid, imperfectly-drained, fermenting mass of mud, teeming with animal and vegetable life, and with a material for which oxygen is the natural ferment; it must be arrested by the hands which drained, or attempted to drain it, and converted into a healthy pasture-land or a wheat-field; if left to nature, centuries might elapse before that which was once a sea would become a healthy forest or natural meadow, during which period man, should he persist in residing on its banks, must undergo the penalty of his own want of knowledge.[71]
CONCLUSION.
In the first chapters of this work I have endeavoured to trace briefly yet succinctly the history of opinion as to the nature of malaria, showing how, prior to the appearance of Macculloch, no one had given to the theory of malaria any definite form. In those which followed I have traced the history of his presumed discovery from the period of its first announcement to its distinct refutation by one of the ablest of statisticians, showing that, notwithstanding this refutation, the physician having, in fact, no other theory to fall back on, persisted in adopting the theory, and, as a natural result, continued to look for and to find in cesspools and ditches, lay-stalls and drains, that unknown and mysterious poison which they had been told by Macculloch was the cause of all diseases. Confounding it with bad odours of all sorts, they sought for remedies in the destruction of bad odours; at times they sealed the sewers and cesspools hermetically and by law: now they opened up and ventilated the sewers and cesspools also by law;[72] and lastly, on finding that they had poisoned the air of the metropolis, and that every experiment they made ended in the precisely opposite results to what they had foretold would happen, as a last resource they endeavour now so to dilute the refuse of living beings as to render it, if possible, inodorous at least. This experiment will also fail. Like true Englishmen, they would not let well alone; they would attempt to solve questions by main force, which science, aided by long and careful experience and observation, could alone effect. At last Liebig appeared, and gave to the whole question a new phasis and another basis; that basis rests on an appeal to the great laws of nature, and not on any researches into the occult, hidden, and mysterious laws regulating the building up and the constructing of the various forms of animal and vegetable life. In this grand work the vital force is in action, whereas the destructive processes by which she annihilates her own forms are strictly chemical; there science may be properly said to commence in respect of the great question I now consider; and uniting experience with observation, it seems to lead to the following conclusions, which, if legitimate, will probably stand their ground until overthrown or modified by the larger experience of succeeding ages.
§ 1. Seeing that putrescent, that is fermentable, bodies can and do exert so great an influence on organic compounds when dead (in the sense we consider them), it is not unreasonable to suppose that animal structures and fluids capable of being fermented, may undergo the same process, that is, fermentation, putrescence, and destruction, or decay, whilst forming a part of the living body.
§ 2. As no sane person doubts the harmony which can be shown to exist in all created beings, so it is probable, if not quite certain, that the laws of decomposition must be as regular as the laws of composition; or, in other words, that as the organic matter is without a doubt the same throughout the living world, and as living bodies are built up or constructed agreeably to certain laws, so, undoubtedly, will they be decomposed by laws equally fixed and constant; invariable; and the nature of the material so decomposed will in no shape be affected by those specific differences which bestow on organic nature her beauteous and varied aspect.
§ 3. The final product, whether of composition or decomposition, must be the same in all respectively; the infusoria, as well as the gigantic whale and elephant, are composed, when living, of the same elementary tissues, and, when dead, decompose into elements the same in all.
§ 4. The presence of microscopic animalcules in putrifying substances is viewed by Liebig as accidental, and not essential to putrefaction or to fermentation; but even admitting this, it is certain that animalcules (infusoria) exist everywhere in inconceivable numbers; if water contains these putrescible substances, as it must always do, then the infusoria are also present in the water; let this water evaporate under the heat of the sun, and we have in a fermentable, that is, putrescible, condition countless myriads of infusoria wafted through the atmosphere, and in certain localities (Pontine Marshes, Sierra Leone, the Orinoco, &c.) forming almost a constant, if not a constituent, part of the atmosphere; they pass into living bodies by respiration: hence the hitherto inexplicable phenomena with regard to the influence of locality in the production of disease, whether derived from animal or vegetable remains.